1 The Mesozoic Era is known as the Age of Reptiles. However, other life forms were also abundant. The oceans were full of marine organisms. Land animals competed for space and food. The food chain had begun.2 Phytoplankton were at the base of the food chain. These are tiny organisms that float near the surface of bodies of water. They use photosynthesis to make their own food.3 Insects were also present during the Mesozoic Era. Fossils of flies and mosquitoes have been found. Wasps and bees were also common. The first birds shared the airways with insects during this era.4 Some predators lived in the water during this era. Ammonites were common in the seas. They were related to octopuses and squids. Other swimming predators included ichthyosaurs. They looked like the dolphins we know today. Other reptiles looked like walruses and seals. These life forms ruled the seas during the Mesozoic Era.5 Other "firsts" that appeared during this time were mammals. A mammal is an animal that is warm blooded. They also feed their young with milk from mammary glands on their bodies. Most have skin that is covered with hair.